Guidewire placement is a critical step in many medical procedures, particularly in minimally invasive procedures and treatment of vascular diseases. For example, a number of vascular diseases, such as coronary artery disease and peripheral vascular disease, are caused by the build-up of fatty atherosclerotic deposits (plaque) in the arteries, which limit blood flow to the tissues that are supplied by that particular artery. Disorders caused by occluded body vessels, including coronary artery disease (CAD) and peripheral artery disease (PAD) may be debilitating and life-threatening. Chronic Total Occlusion (CTO) can result in limb gangrene, requiring amputation, and may lead to other complications and eventually death. Increasingly, treatment of such blockages may include angioplasty or atherectomy procedures in which a guidewire, often via a catheter, is inserted into the diseased artery and threaded to the blocked region. There the blockage may be either squeezed into a more open position, for example, by pressure from an inflated catheter balloon (e.g., balloon angioplasty), and/or the blocked region may be held open by a stent. Alternatively a physician may use a catheter to surgically remove the plaque from the inside of the artery (e.g., an atherectomy).
Thus, placement of a guidewire completely or partially across the occlusion is often a critical, though difficult step. Devices and method for guidewire placement are expensive, complex, and all too often ineffective. A guidewire must typically be forced across or through the occlusion so that the treatment catheter may be positioned to treat the occluding plaque. The guidewire must be positioned across the plaque because the active (e.g., plaque removing or displacing) portions of most currently available catheters are usually located on the sides of the catheters. For example, stents, balloons, atherectomy cutting tools, and other active portions are usually mounted on the sides of the catheter.
However, when the artery is totally blocked by plaque, it is extremely difficult, and potentially dangerous to force the guidewire through the occlusion. An obstruction or plaque may be composed of relatively tough fibrous material, often including hard calcium deposits. Forcing a guidewire or catheter past such obstructions may cause the guidewire to exit the lumen of the vessel (e.g., artery), including causing it to enter the layers forming the artery, further damaging the tissue.
Currently available devices and methods for crossing occlusions are inadequate. For example, patents such as U.S. Pat. No. 5,556,405 to Lary, U.S. Pat. No. 6,152,938 to Curry, and U.S. Pat. No. 6,730,063 to Delaney et al. describe devices and methods for passing an occlusion that do not adequately allow placement of a guidewire across a plaque. U.S. Pat. No. 5,556,405 teaches an incisor catheter having blades that can protrude from the catheter to push outward and form linear cuts in the plaque. Control of this device is mostly limited to extending/retracting the blades, and the cutting edges may damage the tissue, particularly if the blades contact the edges of the vessel; potentially exiting the lumen of the vessel. U.S. Pat. No. 6,152,938 describes a catheter drilling device for opening a wide variety of different blocked (occluded) tubes. The device anchors the tip of the drill head against a face of the occlusion, and partially rotates the drill head using a rein attached to the drill head so that the drill head faces at an angle. The blades of the drill are only controlled in rotation and may cut even non-target tissue, also leading the tip to exit and/or damage the vessel. As one alternative, U.S. Pat. No. 6,730,063 teaches a catheter device that can chemically treat calcified vascular occlusions by delivering acidic solutions and other fluids to calcified plaque to chemically dissolving the calcified material. As in the other known methods, this chemical treatment may be difficult to control, and in particular may be difficult to prevent damage to the vessel. Commercially available devices for treating occluded vessels include those marketed by Cordis Corporation, FlowCardia Technology, Kensey Nash Corporation, and other companies. These devices suffer from the same inadequacies as described above, and have also proven to have only limited success. The best reported success rates of overcoming CTOs with prior art devices range from 56% to 75%.
In addition, many of the devices and methods for crossing an occlusion described above may still require manually forcing the guidewire through the occlusion with only minimal (or no) assistance from the devices. Finally, many of these devices may inadvertently exit the vessel, but few, if any of them, are readily re-positionable to reenter the vessel.
A large family of patents and pending application including U.S. Pat. No. 6,001,112, U.S. Pat. No. 6,454,779, U.S. Pat. No. 6,206,898, U.S. Pat. No. 7,479,147, U.S. Pat. No. 6,451,036, U.S. Pat. No. 6,482,217, U.S. Pat. No. 7,172,610, U.S. Pat. No. 7,235,088 and U.S. Pat. No. 6,666,874 (“Taylor patents”) describe a rotatable cutter that is configured for atherectomy cutting. These devices typically include an inner rotating member (that may extend from a fixed housing at the distal end of the device). The device may be guided by a guidewire, and may include a vacuum source to remove cut material. However, these devices are not adapted to self-center. In addition, these blades are typically side-cutting, meaning that the cutting typically occurs at the sides, where the rotating blade may interact with a (typically fixed) complementary surface, cutting the tissue between the surfaces. Further, the distal rotating cutting head is smaller than the diameter of the rest of the elongate distal portion of the device.
Thus, there remains a need for guidewire positioning devices that can effectively traverse occluded vessels, and particularly chronically occluded vessels. Such devices would enable positioning of a guidewire and therefore enable positioning of stents and other devices to be more successfully used in high occlusion situations, leading to improved patient outcomes and a reduction in patient morbidity and mortality.